Self-aligned protection layer for copper post structure

ABSTRACT

A semiconductor device includes a semiconductor substrate and a conductive post overlying and electrically connected to the substrate. The semiconductor device further includes a manganese-containing protection layer on a surface of the conductive post. The semiconductor device further includes a cap layer over a top surface of the conductive post. A method of forming a semiconductor device includes forming a bond pad region on a semiconductor substrate. The method further includes forming a conductive post overlying and electrically connected to the bond pad region. The method further includes forming a protection layer on a surface of the conductive post, wherein the protection layer comprises manganese (Mn). The method further includes forming a cap layer on a top surface of the conductive post.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. application Ser. No.13/660,348, filed Oct. 25, 2012, which is a continuation application ofU.S. application Ser. No. 12/786,698, filed May 25, 2010, which claimspriority of U.S. Provisional Patent Application Ser. No. 61/238,749filed on Sep. 1, 2009, which are incorporated herein by reference intheir entireties.

TECHNICAL FIELD

This disclosure relates to the fabrication of semiconductor devices, andmore particularly, to bump structures of semiconductor devices.

BACKGROUND

Modern integrated circuits are made up of literally millions of activedevices such as transistors and capacitors. These devices are initiallyisolated from each other, but are later interconnected together to formfunctional circuits. Typical interconnect structures include lateralinterconnections, such as metal lines (wirings), and verticalinterconnections, such as vias and contacts. Interconnections areincreasingly determining the limits of performance and the density ofmodern integrated circuits. On top of the interconnect structures, bondpads are formed and exposed on the surface of the respective chip.Electrical connections are made through bond pads to connect the chip toa package substrate or another die. Bond pads can be used for wirebonding or flip-chip bonding. Wafer level chip scale packaging (WLCSP)is currently widely used for its low cost and relatively simpleprocesses. In a typical WLCSP, interconnect structures are formed onmetallization layers, followed by the formation of under-bump metallurgy(UBM), and the mounting of solder balls.

Flip-chip packaging utilizes bumps to establish electrical contactbetween a chip's I/O pads and the substrate or lead frame of thepackage. Structurally, a bump actually contains the bump itself and aso-called under bump metallurgy (UBM) located between the bump and anI/O pad. An UBM generally contains an adhesion layer, a barrier layerand a wetting layer, arranged in this order on the I/O pad. The bumpsthemselves, based on the material used, are classified as solder bumps,gold bumps, copper pillar bumps and bumps with mixed metals. Recently,copper interconnect post technology is proposed. Instead of using solderbump, the electronic component is connected to a substrate by means ofcopper post. The copper interconnect post technology achieves finerpitch with minimum probability of bump bridging, reduces the capacitanceload for the circuits and allows the electronic component to perform athigher frequencies. However, copper has a tendency to be oxidized duringmanufacturing processes. The oxidized copper post may lead to pooradhesion of the electronic component to a substrate. The poor adhesioncauses serious reliability concerns due to high leakage currents. Theoxidized copper post may also lead to underfill cracking along theinterface of the underfill and the copper post. The cracks may propagateto low-k layers or the solder used to bonding the copper post to thesubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The aforementioned objects, features and advantages of this disclosurewill become apparent by referring to the following detailed descriptionof the preferred embodiments with reference to the accompanyingdrawings, wherein:

FIGS. 1A to 1G are cross-sectional diagram depicting an exemplaryembodiment of a Cu post process;

FIG. 2 is a cross-sectional diagram depicting an exemplary embodiment ofa Cu post structure;

FIGS. 3A to 3C are cross-sectional diagram depicting an exemplaryembodiment of a Cu post process;

FIG. 4 is a cross-sectional diagram depicting an exemplary embodiment ofa Cu post structure;

FIGS. 5A to 5C are cross-sectional diagram depicting an exemplaryembodiment of a Cu post process;

FIG. 6 is a cross-sectional diagram depicting an exemplary embodiment ofa Cu post structure;

FIGS. 7A to 7C are cross-sectional diagram depicting an exemplaryembodiment of a Cu post process; and

FIG. 8 is a cross-sectional diagram depicting an exemplary embodiment ofa Cu post structure.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In the following description, numerous specific details are set forth toprovide a thorough understanding of the disclosure. However, one havingan ordinary skill in the art will recognize that the disclosure can bepracticed without these specific details. In some instances, well-knownstructures and processes have not been described in detail to avoidunnecessarily obscuring the disclosure.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment. Thus, the appearances of the phrases “in oneembodiment” or “in an embodiment” in various places throughout thisspecification are not necessarily all referring to the same embodiment.Furthermore, the particular features, structures, or characteristics maybe combined in any suitable manner in one or more embodiments. It shouldbe appreciated that the following figures are not drawn to scale;rather, these figures are merely intended for illustration.

This disclosure provides a novel integrated circuit structure formed ina copper interconnect post process and methods of forming the same.Throughout this disclosure, the term “copper (Cu) post” refers to acopper protrusion formed over a bond pad, and/or a copper-containingprotrusion formed over an interconnection layer over the bond pad. Asused throughout this disclosure, the term “copper” is intended toinclude substantially pure elemental copper, copper containingunavoidable impurities, and copper alloys containing minor amounts ofelements such as tantalum, indium, tin, zinc, manganese, chromium,titanium, germanium, strontium, platinum, magnesium, aluminum orzirconium.

Herein, cross-sectional diagrams of FIG. 1A to FIG. 1G illustrate anexemplary embodiment of a Cu post structure.

In FIG. 1A, an example of a substrate 10 used for Cu postinterconnection fabrication may comprise a semiconductor substrate asemployed in a semiconductor integrated circuit fabrication, andintegrated circuits may be formed therein and/or thereupon. Thesemiconductor substrate is defined to mean any construction comprisingsemiconductor materials, including, but is not limited to, bulk silicon,a semiconductor wafer, a silicon-on-insulator (SOI) substrate, or asilicon germanium substrate. Other semiconductor materials includinggroup III, group IV, and group V elements may also be used. Theintegrated circuits as used herein refer to electronic circuits havingmultiple individual circuit elements, such as transistors, diodes,resistors, capacitors, inductors, and other active and passivesemiconductor devices.

The substrate 10 further includes inter-layer dielectric layers and ametallization structure overlying the integrated circuits. Theinter-layer dielectric layers in the metallization structure includelow-k dielectric materials, un-doped silicate glass (USG), siliconnitride, silicon oxynitride, or other commonly used materials. Thedielectric constants (k value) of the low-k dielectric materials may beless than about 3.9, or less than about 2.8. Metal lines in themetallization structure may be formed of copper or copper alloys. Oneskilled in the art will realize the formation details of themetallization layers. A conductive region 12 is a top metallizationlayer formed in a top-level inter-layer dielectric layer, which is aportion of conductive routs and has an exposed surface treated by aplanarization process, such as chemical mechanical polishing (CMP), ifnecessary. Suitable materials for the conductive region 12 may include,but are not limited to, for example copper, aluminum, copper alloy, orother mobile conductive materials. In one embodiment, the conductiveregion 12 is a bond pad region 12, which may be used in the bondingprocess to connect the integrated circuits in the respective chip toexternal features.

FIG. 1A also illustrates a passivation layer 14 formed on the substrate10 and patterned to form an opening 15 exposing a portion of theconductive region 12. In one embodiment, the passivation layer 14 isformed of a non-organic material selected from un-doped silicate glass(USG), silicon nitride, silicon oxynitride, silicon oxide, andcombinations thereof. In another embodiment, the passivation layer 14 isformed of a polymer layer, such as an epoxy, polyimide, benzocyclobutene(BCB), polybenzoxazole (PBO), and the like, although other relativelysoft, often organic, dielectric materials can also be used.

Referring to FIG. 1B, an adhesion layer 16 and a seed layer 18 areformed and patterned on a portion of the passivation layer 14 and linethe sidewalls and bottom of the opening 15. Also, a post-passivationinterconnect (PPI) line 22 is formed and patterned on the layers 16 and18 and fills the opening 15. The adhesion layer 16, also referred to asa glue layer, is blanket formed, covering the passivation layer 14 andthe sidewalls and the bottom of opening 15. The adhesion layer 16 mayinclude commonly used barrier materials such as titanium, titaniumnitride, tantalum, tantalum nitride, and combinations thereof, and canbe formed using physical vapor deposition, sputtering, and the like. Theadhesion layer 16 helps to improve the adhesion of the subsequentlyformed copper lines onto passivation layer 14. The seed layer 18 isblanket formed on the adhesion layer 16. The materials of the seed layer18 include copper or copper alloys, and metals such as silver, gold,aluminum, and combinations thereof may also be included. The seed layer18 may also include aluminum or aluminum alloys. In an embodiment, theseed layer 18 is formed of sputtering. In other embodiments, othercommonly used methods such as physical vapor deposition or electrolessplating may be used. For clarity, the seed layer 18 and the adhesionlayer 16 are shown as layers 20 in subsequent drawings.

Using a mask and a photolithography process, a conductive material fillsthe opening of the mask followed by removing the mask and the exposedlayers 20. The conductive material formed on the layer 20 and fillingthe opening 15 serves as the PPI line 22. The PPI line 22 may include,but not limited to, for example copper, aluminum, copper alloy, or othermobile conductive materials. The PPI line 22 may further include anickel-containing layer (not shown) on the top a copper-containinglayer. The PPI formation methods include plating, electroless plating,sputtering, chemical vapor deposition methods, and the like. The PPIline 22 connects the bond pad region 12 to bump features. The PPI line22 may also function as power lines, re-distribution lines (RDL),inductors, capacitors or any passive components. The PPI line 22 mayhave a thickness less than about 30 μm, for example between about 2 μmand about 25 μm. Then the exposed portions of the layers 20 includingthe adhesion layer 16 and the seed layer 18 are removed. The removalstep may include a wet etching process or a dry etching process. In oneembodiment, the removal step includes an isotropic wet etching using anammonia-based acid, which may be a flash etching with a short duration.

Next, in FIG. 1C, a dielectric layer 24, also referred to as anisolation layer or a passivation layer, is formed on the passivationlayer 14 and the PPI line 22. The dielectric layer 24 may be formed ofdielectric materials such as silicon nitride, silicon carbide, siliconoxynitride or other applicable materials. The formation methods includeplasma enhance chemical vapor deposition (PECVD) or other commonly usedCVD methods. Then a polymer layer 26 is formed on the dielectric layer24 through the steps of coating, curing, descum and the like.Lithography technology and etching processes such as a dry etch and/or awet etch process are then performed to pattern the polymer layer 26 andan opening 27 passing through the polymer layer 26 and the dielectriclayer 24, thus exposing a portion of the underlying PPI line 22. Thepolymer layer 26, as the name suggests, is preferably formed of apolymer, such as an epoxy, polyimide, benzocyclobutene (BCB),polybenzoxazole (PBO), and the like, although other relatively soft,often organic, dielectric materials can also be used. In one embodiment,the polymer layer 26 is a polyimide layer. The polymer layer 26 is soft,and hence has the function of reducing inherent stresses on thesubstrate. In addition, the polymer layer 26 can easily be formed tothickness of tens of microns.

In FIG. 1D, the formation of an under-bump-metallurgy (UBM) layer 28includes a diffusion barrier layer and a seed layer is performed on theresulted structure. The UBM layer 28 is formed on the polymer layer 26and the exposed portion of the PPI line 22, and lines the sidewalls andbottom of the opening 27. The diffusion barrier layer, also referred toas a glue layer, is formed to cover the sidewalls and the bottom of theopening 27. The diffusion barrier layer may be formed of tantalumnitride, although it may also be formed of other materials such astitanium nitride, tantalum, titanium, or the like. The formation methodsinclude physical vapor deposition (PVD) or sputtering. The seed layermay be a copper seed layer formed on the diffusion barrier layer. Theseed layer may be formed of copper alloys that include silver, chromium,nickel, tin, gold, and combinations thereof. In one embodiment, the UBMlayer 28 is a Cu/Ti layer.

Next, a mask layer 30 is provided on the UBM layer 28 and patterned withan opening 32 exposing a portion of the UBM layer 28 for bump formation.The opening 32 is over the opening 27. In one embodiment, the diameterof the opening 32 is greater or equal to the diameter of the opening 27.The mask layer 30 may be a dry film or a photoresist film.

Referring to FIG. 1E, the opening 32 is filled with a Cu alloy layer 34.The formation methods may include sputtering, printing, electro plating,electroless plating, and commonly used chemical vapor deposition (CVD)methods. For example, electro-chemical plating (ECP) is carried out toform the Cu alloy layer 34. In one embodiment, the Cu alloy layer 34 isa copper-manganese (CuMn) layer. The ratio of manganese (Mn) to coppercontained in the CuMn layer is not limited. In other embodiments, Ti,Al, Nb, Cr, V, Y, Tc, Re, or the like can be utilized as an additivemetal for forming the Cu alloy layer 34.

Next, as shown in FIG. 1F, the mask layer 30 is removed. In the case themask layer 30 is a dry film, it may be removed using an alkalinesolution. If the mask layer 30 is formed of photoresist, it may beremoved using acetone, n-methyl pyrrolidone (NMP), dimethyl sulfoxide(DMSO), aminoethoxy ethanol, and the like. Then the exposed portion ofthe UBM layer 28 is etched to expose the underlying polymer layer 26outside the Cu alloy layer 34. In an exemplary embodiment, the step ofremoving the UBM layer 28 is a dry etching or a wet etching. Forexample, an isotropic wet etching (often referred to as flash etchingdue to its short duration) using an ammonia-based acid is employed. Thusthe Cu alloy layer 34 protrudes from the polymer layer 26.

Thereafter, in FIG. 1G, Using an annealing process 36, the Mn existed inthe Cu alloy layer 34 diffuses out from the Cu alloy layer 34, and thusthe Cu alloy layer 34 with less Mn refers to a Cu post 34 a. The ratioof Mn to copper contained in the Cu post 34 a is less than the ratio ofMn to copper contained in the Cu alloy layer 34. Also, the diffused-outMn reacts with the annealing ambient to form a protection layer 38 in aself-aligned manner at the surface of the Cu post 34 a. The protectionlayer 38 may be formed at the top surface 34 t and the sidewall surface34 s of the Cu post 34 a. In one embodiment, during an annealing processwith NH₃ or N₂/H₂ ambient, the Mn will react with nitrogen to form amanganese nitride (MnN_(x)) layer as the protection layer 38 in aself-aligned manner at the surface of the Cu post 34 a. Alternatively,during the annealing process 36, copper oxidation layer (CuO_(x)) at thesurface of the Cu post 34 a is reduced, forming a manganese oxide layer,such as MnO_(x) or MnO_(x)N_(y) as the protection layer 38 in aself-aligned manner at the surface of the Cu post 34 a. The protectionlayer 38 can lower resistance and prevent copper diffusion to enhanceback end of the line (BEOL) performance. Moreover, the protection layercan improve the adhesion between the Cu post 34 a formed by ECP methodand the underlying Cu layer formed by PVD method, and thus the Cupeeling issue can be suppressed. Further, the protection layer 38 formedin a self-aligned manner can prevent openings existed in the dielectriclayer adjacent the bottom of the opening, thus solving the contactissue. These can improve package capabilities.

The substrate 10 may then be sawed and packaged onto a packagesubstrate, or another die, with solder balls or Cu posts mounted on apad on the package substrate or the other die.

FIG. 1F is a cross-sectional diagram illustrating an exemplaryembodiment of a Cu post 34 a with the surface protection layer 38 formedoverlying the PPI line 22 that is electrically connected to the bond padregion 12. FIG. 2 is a cross-sectional diagram illustrating an exemplaryembodiment of the Cu post 34 a with a surface protection layer 38overlying and electrically connecting the bond pad region 12, whileexplanation of the same or similar portions to the description in FIG.1G will be omitted. As depicted in FIG. 2, the UBM layer 28 is formed onthe sidewalls and bottom of the opening 15 in the passivation layer 14,and the Cu post 34 a is formed on the UBM layer 28 to fill the opening15 and protrude from the passivation layer 14. The protection layer 38is formed in a self-aligned manner on the top surface and the sidewallsurface of the Cu post 34 a. Thus the Cu post 34 a and the UBM layer 28are formed directly on the bond pad region 12.

FIG. 3A to FIG. 3C are cross-sectional diagrams depicting an exemplaryembodiment of a Cu post structure with a cap layer, while explanation ofthe same or similar portions to the description in FIG. 1A to FIG. 1Gwill be omitted.

Referring to FIG. 3A, after forming the Cu alloy layer 34 in the opening32 of the mask layer 30, a cap layer 40 is deposited on the Cu alloylayer 34 within the opening 32. The cap layer 40 could act as a barrierlayer to prevent copper in the Cu post 24 a to diffuse into bondingmaterial, such as solder ball, that is used to bond the substrate 10 toexternal features. The prevention of copper diffusion increases thereliability and bonding strength of the package. The cap layer 40 mayinclude nickel, tin, tin-lead (SnPb), gold (Au), silver, palladium (Pd),In, nickel-palladium-gold (NiPdAu), nickel-gold (NiAu), other similarmaterials, or alloy. In one embodiment, the cap layer 40 is a lead-freepre-solder layer, for example, SnAg. In another embodiment, the caplayer 40 is a solder material including alloys of tin, lead, silver,copper, nickel, bismuth, or combinations thereof. In the otherembodiment, the cap layer 40 is a nickel layer, an Au layer, or a NiAulayer. After removing the mask layer 30 and the UBM layer 28 no coveredby the Cu alloy layer 34 as depicted in FIG. 3B, the annealing process36 is performed to form the protection layer 38 in a self-aligned mannerat the sidewall surface 34 t of the Cu post 34 a. The protection layer38 may be a manganese nitride (MnN_(x)) layer, or a manganese oxidelayer, such as MnO_(x) or MnO_(x),N_(y).

FIG. 4 is a cross-sectional diagram illustrating an exemplary embodimentof the Cu post 34 a with a surface protection layer 38 and a cap layer40 overlying and electrically connecting the bond pad region 12. The UBMlayer 28 is formed on the sidewalls and bottom of the opening 15 in thepassivation layer 14, and the Cu post 34 a is formed on the UBM layer 28to fill the opening 15 and protrude from the passivation layer 14. Theprotection layer 38 is formed in a self-aligned manner on the sidewallsurface of the Cu post 34 a. The cap layer 40 is formed on the topsurface of the Cu post 34 a. Thus the Cu post 34 a and the UBM layer 28are formed directly on the bond pad region 12.

FIG. 5A to FIG. 5C are cross-sectional diagrams depicting an exemplaryembodiment of a Cu post structure, while explanation of the same orsimilar portions to the description in FIG. 1A to FIG. 1G will beomitted.

Referring to FIG. 5A, after the formation of the opening 27 in thepolymer layer 26 as depicted in FIG. 1C, an under-bump-metallurgy (UBM)layer 28 a including a diffusion barrier layer is formed on the resultedstructure. The UBM layer 28 a is formed on the polymer layer 26 and theexposed portion of the PPI line 22, and lines the sidewalls and bottomof the opening 27. The diffusion barrier layer, also referred to as aglue layer, may be formed of tantalum nitride, although it may also beformed of other materials such as titanium nitride, tantalum, titanium,or the like. In one embodiment, the UBM layer 28 a is a Ti layer.

Next, a Cu ally film 29 is deposited on the UBM layer 28 a, lining thesidewalls and bottom of the opening 27. The formation methods mayinclude sputtering, printing, electro plating, electroless plating, andcommonly used chemical vapor deposition (CVD) methods. In oneembodiment, the Cu alloy film 29 is a copper-manganese (CuMn) layer. Theratio of manganese (Mn) to copper contained in the CuMn layer is notlimited. In other embodiments, Ti, Al, Nb, Cr, V, Y, Tc, Re, or the likecan be utilized as an additive metal for forming the Cu alloy film 29.For example, forming the Cu alloy film 29 with the concentrationgradient of the Mn as described above by a physical method, such assputtering like a PVD (physical vapor deposition), may be considered.

Thereafter, the mask layer 30 with the opening 32 is provided on the Cualloy film 29, and then a copper deposition process, for exampleelectro-chemical plating (ECP) is carried out to form a Cu layer 42 onthe Cu alloy film 29 and fill the opening 32. Thus the underlying bondpad region 12 can be electrically connected to the Cu layer 42. The Culayer 42 includes substantially pure elemental copper, copper containingunavoidable impurities, and copper alloys containing minor amounts ofelements such as tantalum, indium, tin, zinc, manganese, chromium,titanium, germanium, strontium, platinum, magnesium, aluminum orzirconium. In FIG. 5B, the mask layer 30 is removed to make the Cu layer42 protrude from the polymer layer 26 to become a Cu post 42 a. Then theexposed portion of the Cu alloy film 29 and the UBM layer 28 a is etchedto expose the underlying polymer layer 26.

In FIG. 5C, using an annealing process 36, the Mn existed in the Cualloy film 29 diffuses out to decrease the Mn ratio to Cu in the Cualloy film 29. Also, the out-diffused Mn reacts with the annealingambient to form a protection layer 38 in a self-aligned manner at thesurface of the Cu post 42 a. In one embodiment, the UBM layer underlyingthe Cu post 42 a becomes an UBM layer 28 b including the diffusionbarrier layer 28 a and a copper layer after the self-aligned protectionformation. In other embodiments, Mn may remain in the UBM layer 28 b.

The protection layer 38 may be formed at the top surface 42 t and thesidewall surface 42 s of the Cu post 42 a. In one embodiment, during anannealing process with NH₃ or N₂/H₂ ambient, the Mn will react withnitrogen to form a manganese nitride (MnN_(x)) layer as the protectionlayer 38 in a self-aligned manner at the surface of the Cu post 42 a.Alternatively, during the annealing process 36, copper oxidation layer(CuO_(x)) at the surface of the Cu post 42 a is reduced, forming amanganese oxide layer, such as MnO_(x) or MnO_(x)N_(y) as the protectionlayer 38 in a self-aligned manner at the surface of the Cu post 42 a.The protection layer 38 can lower resistance and prevent copperdiffusion to enhance BEOL SPICE performance. Moreover, the protectionlayer can improve the adhesion between the Cu post 42 a formed by ECPmethod and the underlying Cu layer formed by PVD method, and thus the Cupeeling issue can be suppressed. Further, the protection layer 38 formedin a self-aligned manner can prevent openings existed in the dielectriclayer adjacent the bottom of the opening, thus solving the contactissue. These can improve package capabilities.

FIG. 6 is a cross-sectional diagram illustrating an exemplary embodimentof the Cu post 42 a with a surface protection layer 38 overlying andelectrically connecting the bond pad region 12, while explanation of thesame or similar portions to the description in FIG. 5A to FIG. 5C willbe omitted.

FIG. 7A to FIG. 7C are cross-sectional diagrams depicting an exemplaryembodiment of a Cu post structure with a cap layer, while explanation ofthe same or similar portions to the description in FIG. 5A to FIG. 5Cwill be omitted.

Referring to FIG. 7A, after forming the Cu layer 42 in the opening 32 ofthe mask layer 30, a cap layer 40 is deposited on the Cu layer 42 withinthe opening 32. The cap layer 40 could act as a barrier layer to preventcopper in the Cu post 42 a to diffuse into bonding material, such assolder ball, that is used to bond the substrate 10 to external features.The prevention of copper diffusion increases the reliability and bondingstrength of the package. The cap layer 40 may include nickel, tin,tin-lead (SnPb), gold (Au), silver, palladium (Pd), indium (In),nickel-palladium-gold (NiPdAu), nickel-gold (NiAu) or other similarmaterials or alloy. In one embodiment, the cap layer 40 is a lead-freepre-solder layer, for example, SnAg. In another embodiment, the caplayer 40 is a solder material including alloys of tin, lead, silver,copper, nickel, bismuth, or combinations thereof. In the otherembodiment, the cap layer 40 is a nickel layer, an Au layer, or a NiAulayer. After removing the mask layer 30 and the exposed UBM layer 28 aand the Cu alloy film 29 as depicted in FIG. 7B, the annealing process36 is performed to form the protection layer 38 in a self-aligned mannerat the sidewall surface 42 t of the Cu post 42 a. The protection layer38 may be a manganese nitride (MnN_(x)) layer, or a manganese oxidelayer, such as MnO_(x) or MnO_(x)N_(y).

FIG. 8 is a cross-sectional diagram illustrating an exemplary embodimentof the Cu post 42 a with a surface protection layer 38 and a cap layer40 overlying and electrically connecting the bond pad region 12.

One aspect of this description relates to a semiconductor device. Thesemiconductor device includes a semiconductor substrate and a conductivepost overlying and electrically connected to the substrate. Thesemiconductor device further includes a manganese-containing protectionlayer on a surface of the conductive post. The semiconductor devicefurther includes a cap layer over a top surface of the conductive post.

Another aspect of this description relates to a method of forming asemiconductor device. The method includes forming a bond pad region on asemiconductor substrate. The method further includes forming aconductive post overlying and electrically connected to the bond padregion. The method further includes forming a protection layer on asurface of the conductive post, wherein the protection layer comprisesmanganese (Mn). The method further includes forming a cap layer on a topsurface of the conductive post prior to forming the protection layer.

Still another aspect of this description relates to a method of forminga semiconductor device. The method includes forming a bond pad region ona semiconductor substrate. The method further includes forming aconductive post overlying and electrically connected to the bond padregion, the conductive post comprising a copper-manganese alloy. Themethod further includes forming a manganese-containing protection layeron sidewalls of the conductive post. The method further includes forminga cap layer over a top surface of the conductive post

In the preceding detailed description, the disclosure is described withreference to specifically exemplary embodiments thereof. It will,however, be evident that various modifications, structures, processes,and changes may be made thereto without departing from the broaderspirit and scope of the disclosure, as set forth in the claims. Thespecification and drawings are, accordingly, to be regarded asillustrative and not restrictive. It is understood that the disclosureis capable of using various other combinations and environments and iscapable of changes or modifications within the scope of the inventiveconcepts as expressed herein.

What is claimed is:
 1. A semiconductor device, comprising: asemiconductor substrate; a conductive post overlying and electricallyconnected to the substrate; a manganese-containing protection layer on asurface of the conductive post; and a cap layer over a top surface ofthe conductive post.
 2. The semiconductor device of claim 1, furthercomprising an under bump metallurgy (UBM) layer between the conductivepost and the semiconductor substrate, wherein an entirety of a topsurface of the UBM layer is covered by the conductive post.
 3. Thesemiconductor device of claim 1, further comprising an alloy layerbetween the conductive post and the semiconductor substrate, wherein anentirety of a top surface of the alloy layer is covered by theconductive post.
 4. The semiconductor device of claim 1,manganese-containing protection layer comprises MnN_(x), MnO_(x) orMnO_(x)N_(y).
 5. The semiconductor device of claim 1, wherein the caplayer comprises at least one of nickel, tin, tin-lead, gold, bismuth,silver, palladium, indium, nickel-palladium-gold, or nickel-gold.
 6. Thesemiconductor device of claim 1, wherein the cap layer compriseslead-free solder.
 7. The semiconductor device of claim 1, wherein thecap layer directly contacts a top surface of the conductive post. (FIG.8)
 8. A method of forming a semiconductor device, the method comprising:forming a bond pad region on a semiconductor substrate; forming aconductive post overlying and electrically connected to the bond padregion; forming a protection layer on a surface of the conductive post,wherein the protection layer comprises manganese (Mn); and forming a caplayer on a top surface of the conductive post prior to forming theprotection layer.
 9. The method of claim 8, further comprising: formingan under bump metallurgy (UBM) layer between the conductive post and thesemiconductor substrate; etching the UBM layer using the conductive postas a mask.
 10. The method of claim 8, further comprising: forming analloy layer between the conductive post and the semiconductor substrate;etching the alloy layer using the conductive layer as a mask.
 11. Themethod of claim 8, further comprising reducing an oxide layer on theconductive post.
 12. The method of claim 11, wherein the reducing theoxide layer is performed simultaneously with forming the protectionlayer.
 13. The method of claim 8, wherein forming the cap layercomprises forming the cap layer comprising at least one of nickel, tin,tin-lead, gold, bismuth, silver, palladium, indium,nickel-palladium-gold, or nickel-gold.
 14. The method of claim 8,wherein forming the cap layer comprises forming the cap layer comprisinglead-free solder.
 15. The method of claim 8, wherein forming the caplayer comprises forming the cap layer directly on the conductive post.16. A method of forming a semiconductor device, the method comprising:forming a bond pad region on a semiconductor substrate; forming aconductive post overlying and electrically connected to the bond padregion, the conductive post comprising a copper-manganese alloy; forminga manganese-containing protection layer on sidewalls of the conductivepost; and forming a cap layer over a top surface of the conductive post.17. The method of claim 16, further comprising: forming an under bumpmetallurgy (UBM) layer between the conductive post and the bond padregion; and etching the UBM layer using the conductive post as a mask.18. The method of claim 16, further comprising: forming an alloy layerbetween the conductive post and the bond pad region; and etching thealloy layer using the conductive layer as a mask.
 19. The method ofclaim 16, further comprising reducing an oxide layer on the conductivepost.
 20. The method of claim 19, wherein the reducing the oxide layeris performed simultaneously with forming the manganese-containingprotection layer.